title: The effects of different doses of estradiol (E2) on cerebral ischemia in an in vitro model of oxygen and glucose deprivation and reperfusion and in a rat model of middle carotid artery occlusion.
abstract: BACKGROUND
  Because neuroprotective effects of estrogen remain controversial, we aimed to investigate the effect of different doses of estradiol (E2) on cerebral ischemia using both in vivo and in vitro experiments.
  
  
  RESULTS
  PC12 cells were cultured at physiological (10 nM and 20 nM) or pharmacological (10 μM and 20 μM) dosages of E2 for 24 hours (h). The results of 5-bromodeoxyuridine (Brdu) incorporation and flow cytometric analysis showed that physiological doses of E2 enhanced cell proliferation and pharmacological doses of E2 inhibited cell proliferation. After the cells were exposed to oxygen and glucose deprivation (OGD) for 4 h and reperfusion for 20 h, the results of 3-(4, 5-dimethylthiazol-2-yl) 2, 5-diphenyl tetrazolium bromide (MTT) assay, lactate dehydrogenase (LDH) release assay, flow cytometric analysis and Western blot analysis showed that physiological doses of E2 enhanced cell viability, reduced cell apoptosis and decreased the expression of pro-apoptotic protein caspase-3. In contrast, pharmacological doses of E2 decreased cell viability and induced cell apoptosis. In vivo, adult ovariectomized (OVX) female rats received continuous subcutaneous injection of different doses of E2 for 4 weeks. Transient cerebral ischemia was induced for 2 h using the middle cerebral artery occlusion (MCAO) technique, followed by 22 h of reperfusion. The results of Garcia test, 2, 3, 5-triphenyltetrazolium chloride (TTC) staining showed that 6 μg/kg and 20 μg/kg E2 replacement induced an increase in neurological deficit scores, a decrease in the infarct volume and a reduction in the expression of caspase-3 when compared to animals in the OVX group without E2 treatment. However, 50 μg/kg E2 replacement treatment decreased neurological deficit scores, increased the infarct volume and the expression of caspase-3 when compared to animals in the control group and 6 up/kg or 20 μg/kg E2 replacement group.
  
  
  CONCLUSIONS
  We conclude that physiological levels of E2 exhibit neuroprotective effects on cerebral ischemia; whereas, pharmacological or supraphysiological doses of E2 have damaging effects on neurons after cerebral ischemia.
authors.affiliation: Department of Anesthesiology, Xijing Hospital, The Fourth Military Medical University, Xi'an 710032, P R China. gangwuhou@163.com.
authors.forename: Yu-Long
authors.initials: YL
authors.lastname: Ma
authors.forename: Pei
authors.initials: P
authors.lastname: Qin
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.forename: Lan
authors.initials: L
authors.lastname: Shen
authors.forename: Shi-Quan
authors.initials: SQ
authors.lastname: Wang
authors.forename: Hai-Long
authors.initials: HL
authors.lastname: Dong
authors.forename: Wu-Gang
authors.initials: WG
authors.lastname: Hou
authors.forename: Li-Ze
authors.initials: LZ
authors.lastname: Xiong
mesh_terms: D000818:Animals; D015153:Blotting, Western; D001921:Brain / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D002545:Brain Ischemia / Q000378:metabolism / Q000473:pathology; D053148:Caspase 3 / Q000032:analysis / Q000096:biosynthesis; D002470:Cell Survival / Q000187:drug effects; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000008:administration & dosage*; D005260:Female; D005434:Flow Cytometry; D020244:Infarction, Middle Cerebral Artery / Q000378:metabolism / Q000473:pathology*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D018696:Neuroprotective Agents / Q000008:administration & dosage*; D016716:PC12 Cells; D051381:Rats; D017207:Rats, Sprague-Dawley; D020127:Recovery of Function / Q000187:drug effects; D015427:Reperfusion Injury / Q000378:metabolism / Q000473:pathology
chemical_list: D018696:Neuroprotective Agents; D004958:Estradiol; D053148:Caspase 3